Doctor of Philosophy, Case Western Reserve University, 2020, Macromolecular Science and Engineering

With the fast development of modern society, the need for more advanced polymeric materials is increasing at a fast speed. This dissertation focuses on the study of the presence of extensional flows in common plastics processing operations, mainly in single- and twin-screw extrusion, specifically for polyamide-based blends. Twin-screw extruders are one of the most commonly used processing equipment when a mixing task for polymer processing is presented, and as such there is much interest in the investigation of their overall mixing capacities. Shear flows are inferior in mixing efficiency when compared to extensional flows. Kneading blocks (KB) make up the majority of the mixing profile of a typical twin-screw extruder screw, and while there are extensional flow components present in their mixing operations, the main mixing mechanism in these elements is still shear dominated. Considering this, extensional mixing elements (EME) for single- and twin-screw extrusion were recently developed for the purposes of imposing extension dominated flow during twin-screw extrusion and therefore increase the mixing capabilities of current mixing and processing equipment. This thesis explores the potential use of these EMEs in the improvement of morphology and properties of polyamide-based blends. In chapter 1, the design of extension mixing elements will be briefly introduced and the experimental validation of the design using Polystyrene/Polypropylene blends system will be reported. In chapter 2, the effect of extensional mixing elements on reactive extrusion and on the crystalline phase change of polyamide-6 phase in polyamide-6/polystyrene reactive twin screw extrusion system is discussed. The possibility of achieving similar crystalline phase change of polyamide-6 in polyamide-6/polystyrene reactive single-screw extrusion will be discussed in chapter 3 as a supplemental experimental validation and discussion of the effect of extension mixing elements on the reactive extrus (open full item for complete abstract)

Doctor of Philosophy, The Ohio State University, 2020, Oral Biology

Background and Objective: Dental implants are commonly made out of titanium or titanium alloys. The expected outcome following dental implant placement surgery is rigid stability due to osseointegration, the bone remodeling at bone/implant fixture interface, and a mucosal seal characterized by the formation of thin junctional epithelium covering the underlying connective tissue at the alveolar crest. A significant number of studies have been published focusing on post-implantation bone healing and various phases of osseointegration. However, limited amount of information is available regarding the formation and long-term integrity of the soft tissue seal. To understand the role of implant properties on soft-tissue responses, a biomimetic model of human gingiva with and without characteristic peri-implantitis is needed. This thesis is aimed to develop a healthy and “diseased” in vitro gingival model system and utilize our well-established clinical model to investigate the peri-implant soft tissue seal, tissue inflammation, and tissue breakdown in various oral-related conditions. Material and Methods: This thesis has three components addressing three specific aims. Following Introduction in Chapter 1, Chapter 2 presents experimental data on the behavior of gingival fibroblasts and epithelial cells on titanium surfaces with different characteristics in the absence and presence of a challenge from supernatants from P.gingivalis biofilm. Chapter 3 reports methodology of engineering gingiva in vitro by the use of gingival fibroblasts and epithelial cells, in a prototype scaffold used for engineering skin. Chapter 4 describes a clinical study conducted by recruiting 77 patients with implant supported dental restorations. These implants were functional at least for 1 year and revealed possible associations between clinical presentation of healthy/diseased peri-implant soft tissue and site-specific cytokine and titanium release. Results: Studies conducted with cultures es (open full item for complete abstract)

Doctor of Engineering, University of Dayton, 2020, Mechanical Engineering

The mixing industry has long depended on scaled down experimental methods combined with computational analysis to determine rotating mixer designs for customer applications. Most industrial mixing companies have the capabilities in-house to perform these experiments and the analysis to show customers the benefits of proposed designs. Experimental methods center around the calculation of power draw of the mixing unit, determined from a simple torque cell to determine power draw, and the blend time, shown through acid-base neutralization, which are both fairly simple to calculate from an scaled down rig and apply it to either customer designs or in the development of new mixers. The computational analysis centers around research done by mixing forefathers who developed methodology to calculate time dependent mixing parameters, like blend time, through steady state analysis due to restrictions in computational capacity. This is possible because the majority of the mixing can be observed from studying the macro-scale interactions. The impellers and baffles in a tank drive large scale motion which blends two different species or temperatures together to create a uniform mixture. Similar to rotating mixers, there are two main parameters used when analyzing static mixers. Similar to power draw for rotating mixers, static mixers are driven by the pressure drop across the mixer. The second parameter that is used to determine the effectiveness of a static mixer is the coefficient of variation, a statistical measurement of the degree of uniformity. This looks at a two-dimensional plane located downstream from the mixer outlet and determines the effectiveness of the mixer. This has been used for decades to provide the target for customer designs, but it provides a limited picture of the process. The snap shot on a two-dimensional plane provides a small window into what is happening in the entire process. The coefficient of variation also is merely a statistical paramete (open full item for complete abstract)

Doctor of Philosophy (PhD), Wright State University, 2020, Engineering PhD

The unique properties of graphene have directed researchers to study and characterize this new material. Graphene production and graphene based materials have been widely explored and developed in the past decade. Most research has aimed at developing scalable, environmentally friendly, and cheap procedures to produce defect-free graphene that can be used in various applications such as mechanical properties enhancement and multifunctional material. The challenge is processing such material on a scale suitable for engineering applications such as advanced photonics and advanced electronics. In this study, we investigate a new processing technique based on Langmuir-Blodgett (LB) Technique. We managed to produce a mono-graphene film as well as a multilayer graphene film. Besides, we investigate graphene-graphite transition by measuring the electrical conductivity of the produced film. Moreover, we managed graphene/ Poly-methyl methacrylate (PMMA) nanocomposite with thickness up to a few nanometers. We characterized the mechanical, optical, and electrical properties of such films and compared the performance to similar material processed by more expensive film preparation methods.

Master of Science in Mechanical Engineering (MSME), Wright State University, 2020, Mechanical Engineering

This thesis work introduces a novel multi-fidelity modeling framework, which is designed to address the practical challenges encountered in Aerospace vehicle design when 1) multiple low-fidelity models exist, 2) each low-fidelity model may only be correlated with the high-fidelity model in part of the design domain, and 3) models may contain noise or uncertainty. The proposed approach approximates a high-fidelity model by consolidating multiple low-fidelity models using the localized Galerkin formulation. Also, two adaptive sampling methods are developed to efficiently construct an accurate model. The first acquisition formulation, expected effectiveness, searches for the global optimum and is useful for modeling engineering objectives. The second acquisition formulation, expected usefulness, identifies feasible design domains and is useful for constrained design exploration. The proposed methods can be applied to any engineering systems with complex and demanding simulation models.

Master of Science, The Ohio State University, 2020, Aero/Astro Engineering

Non-self-sustained hybrid plasmas are formed by the overlap of two separate voltage waveforms with significantly different reduced electric field values (E/N), one of them below the ionization threshold, to produce excited species and radicals selectively. In this work, a stable, capacitively coupled ns pulse – RF waveform hybrid discharge is operated in nitrogen and mixtures of nitrogen with other molecular gases at 50 – 100 Torr pressure, using a single pair of electrodes mounted externally to the reactor cell. The purpose of the ns pulse discharge is to generate ionization and electronic excitation of the mixture components, while the below-breakdown RF voltage couples additional energy to the vibrational modes of the mixture components. Based on the broadband plasma emission imaging, the plasma volume appears to be enhanced by the RF waveform, compared to ns pulse discharge, due to the drift oscillations of electrons induced by the RF waveform. Coherent Anti-Stokes Raman Spectroscopy (CARS) measurements in the hybrid discharge operated in nitrogen show that the RF waveform significantly enhances the vibrational excitation of N2 in the ground electronic state, populating vibrational levels up to at least v=3, and increasing the vibrational temperature of N2 from TV = 1210 ± 110 K in the ns pulse train plasma to TV = 1810 ± 170 K in the ns-RF hybrid discharge. The translational- rotational temperature at these conditions remains low, TR = 315 ± 15 K. To evaluate the potential of this plasma to operate in other gas mixtures, 1% of H2 is added to nitrogen. CARS measurements reveal a moderate N2 vibrational relaxation by hydrogen, reducing the vibrational temperature in the hybrid plasma to TV = 1700 ± 150 K and increasing in the translational-rotational temperature to TR = 396 ± 10 K. Time-resolved measurements of the number density of the first electronically excited state of nitrogen, N2(A3Σ), obtained using Tunable Diode Laser Absorption Spectroscopy (TDLAS) in n (open full item for complete abstract)

Doctor of Philosophy, The Ohio State University, 2020, Civil Engineering

Vibration-based structural health monitoring (SHM) has become increasingly popular in recent years as a general and global method to detect possible damage scenarios. With the increase in the number of infrastructures that are in service beyond their initial design service age, more and more owners are relying on SHM to evaluate the integrity of their structures. As a result, SHM approaches that are applicable to a variety of structures with minimal service interruption and lower cost are of high importance. There are many research on SHM processes using a network of sensors placed on over a target structure. Although these approaches may result in more accurate results due to redundancy of the system, they are mostly cost prohibitive for currently in-service structures and are suitable for newly constructed projects with embedded sensors. This dissertation presents a feature-based SHM process using a new signal processing and feature extraction methodology and presents its application on a real-life vibration monitoring project completed of an energized substation structure. The new signal processing and feature extraction methodology uses specific filtering and optimization schemes which improved the performance in extracting features specifically when using a contaminated response signal. Next, the extracted features are used in a structural model updating to identify and localize the damage through an optimization process. Finally, a vortex-induced vibration analysis process is presented and applied to the real-life monitored structure. Currently there are no power utility industry standard methodology for the analysis and design of structures against wind-induced vibrations. The current codes or standards of practice recommend using damping devices such as chain dampers or strakes to mitigate the vibrations, when they are observed. This approach may not be feasible due to the energized in-service structures. In addition, modifications to the installed structure (open full item for complete abstract)

Master of Science (MS), Ohio University, 2020, Industrial and Systems Engineering (Engineering and Technology)

Process improvements in hospitals usually focus on a single department (eg. emergency department, operating theater, specialty clinic, etc). However, actions taken in one department inevitably affect the performance of other departments. Therefore, higher efficiency improvements can be obtained by considering the patient care process as one synergetic activity involving several departments and various sets of resources. In this research we propose an integrated approach for modeling the patient lifecycle for multiple departments. First we describe a patient flow from his/her entry into the hospital through a progressive care unit until the patient has fully recovered. We use process mapping methods to address value added activities and other necessary activities in the patient lifecycle. Then, a simulation model is developed in Simio using customized objects created in previous works. Those customized objects carry their own logic and behavior. For example, the Bed object includes logic for a patient recovering while using several hospital resources (nurses, therapist) in his/her hospital stay. Those objects were used to build several configurations of an integrated model with multiple departments. Data about patient arrival patterns, their health acuity, and procedure needs were obtained from a real hospital in order to test our approach. The procedures duration data (which were different for different levels of patient acuity and for different surgical and other procedures) were used to obtain service distribution using statistical analysis methods. Modular simulation objects and data distributions from real hospitals allowed us to build an integrated simulation model with several configurations of the process flow. Simulation experiments were performed on these models and performance recorded. The recommendation for implementations in the hospitals is also reported.

Doctor of Philosophy, The Ohio State University, 2020, Electrical and Computer Engineering

DC distribution networks have found increased applications in electric automobiles, ships, aircrafts, server farms, and EV charging stations. These networks contain load regulating power electronic converters such as dc-dc and dc-ac converters that act as Constant Power Loads (CPLs). When these CPLs interact with the dc system, they can cause destabilizing effects on the grid due to their negative incremental impedance. Preliminary studies have performed stability analysis of dc distribution systems and proposed passive stabilization and source/load converter level controlstrategies to address the instability issue which does not address all the stability issues of multi-terminal dc distribution systems. In this research, a method to dynamically stabilize CPLs at the point of load by making them behave as adaptive Smart Resistors using high bandwidth power converters and energy storage units has been proposed. By utilizing high bandwidth power converters, these Smart Resistors can work with smart sources to realize ultimate intelligent power networks. This research aims to identify the realization of the smart Resistor concept and its utilization in the control of dc distribution systems. The effect of the Smart Resistor on the stability of various configurations of dc distribution networks are studied. The aims of this research study are as follows: The control strategies needed to achieve the Smart Resistor concept. The trajectory control of the system during voltage and current transients are studied. The energy management of energy storage is also proposed. The interaction of a constant power load powered by an ideal voltage source and a case study of a traction drive system is performed and the small and large-signal stability of the system is analyzed. The stability of a non-ideal source power converter feeding a constant power load. A case study of a section of a turbo-electric aircraft is used to showcase how the CPL (open full item for complete abstract)

Doctor of Philosophy, The Ohio State University, 2020, Electrical and Computer Engineering

Two research areas in the field of biomedical engineering that have progressed significantly and garnered a great deal of interest in recent years are electroporation and biosensors. Electroporation has found wide usage in microbiology and cellular manipulation. Conventional or “bulk” electroporation (BEP) is the most commonly employed electroporation technique, and while it is easy to use and able to transfect a large cell population, it suffers a variety of drawbacks such as high voltage levels (resulting in low transfection efficiency due to cellular damage) and non-uniform biasing applied to the target cell population. 2D Micro-electroporation (MEP) and its successor 2D nano-electroporation (NEP) allow for control over delivery dosage and uniform biasing of target cell populations, but at low throughput. The first portion of this Ph. D. research uses Bosch etching process, which is optimized and characterized with respect to etch rate, etching parameters, and feature size to create a 3D NEP silicon platform that conserves the best attributes of both 2D NEP and BEP. Before device fabrication, a Bosch etching process is optimized and characterized with respect to etch rate, etching parameters, and feature size. The 3D NEP device is evaluated to ensure it possesses the “hallmark” benefits of NEP such as dosage control, good transfection uniformity, and high cell viability in a high throughput system. Simulations are performed and corresponding experiments are run to determine the ideal voltage for optimizing these parameters. As a result of this research the following have been achieved, (1) a tracked-etched membrane (which suffered from randomized nano-channel locations and thus poor throughput) is no longer the only available 3D NEP-style system. (2) The design and creation of this 3D NEP device allows the user to have dosage control, high cell viability, and uniform transfection for a large cell population. (3) A high-throughput 3D NEP system is (open full item for complete abstract)

Master of Science, The Ohio State University, 2020, Mechanical Engineering

Advanced Driver Assistance Systems (ADAS) and Automated Driving Systems (ADS) are ushering in a new era of transportation innovation and safety by incorporating technologies aimed at making the driving experience safer, more efficient, and comfortable. They assist in performing complex maneuvers, preempt potential risky situations, and take over the driver's tasks in critical situations. Innovation acceptance research for ADAS show that the increasing demand for safety and comfort are the two key prime movers of ADAS market. Hence, there is a need to comprehensively test for both during the process of product verification and validation. Due to complexity of the system, cost of testing and safety of the test engineers, a significant part of ADAS/ADS algorithms validation needs to be done virtually. Although simulation-based validation and verification (V&V) is not new, the requirements of test descriptions and software tools are not yet well understood. This project builds around the process of simulation for testing by exposing ADAS/ADS software to pre-defined scenarios. Different scenarios are built in a series of virtual simulators which have unique features, methods and assumptions that must be well-understood for the results to be proven valid. These essential features of the simulators are documented to understand the effect of simulator specific scenario parameters on simulation results. For the perceived safety and comfort aspect of ADAS, objective assessment of the Lane Keep Assist feature is performed which involves a MATLAB®-based tool for giving a scalar rating to the performance of the Lane Keep Assist system. For a series of simulations, the essential drive quality parameters and the corresponding “goodness score” ratings of ADAS based on suitable metrics are used to train and develop a Machine learning algorithm that gives a quality assessment of the Lane Keep Assist system. Finally, a methodology is proposed that can be used to perform the same asse (open full item for complete abstract)

Master of Science in Engineering, Youngstown State University, 2020, Department of Mechanical, Industrial and Manufacturing Engineering

Wind tunnels continue to be essential for testing aerodynamic systems and underlying flow physics required in research and industry for proper modeling and design. This study introduces the newly reconstructed low-speed, research-grade boundary-layer wind tunnel constructed at Youngstown State University and first measurements of performance to support computational modeling of experiments. The tunnel design is based on a facility that previously existed in the Fluid Mechanics Laboratory at the NASA Ames Research Center that contributed validation experiments for direct numerical simulation (DNS) of non-trivial flows in the 1990s. In this work, the newly-built tunnel was calibrated and a flow quality survey was conducted, which included measurements of cross-section uniformity, boundary-layer measurements, and turbulence intensity. Measurements were performed at operating speeds of 3, 7.5, 15, and 30 m/s. Prior to construction, computational modeling of the facility had been performed and estimated that a 40 hp blower would provide the desired operating speed envelope and maximum speed of 40 m/s. It was found that the top speed of the wind tunnel with an empty test-section was 35 m/s. The cross-sectional flow nonuniformity, measured with the Pitot-static tube, showed a maximum difference of 3% from the centerline velocity in the upper half of the speed range. The natural boundary-layer state was measured using a fine Pitot-tube and compared to 3-D, Reynolds-averaged flow calculations and well-known velocity profile benchmarks from laminar incompressible theory (Blasius solution for zero-pressure-gradient-flow) and the turbulent 1/7th power law. The results showed good agreement with the laminar profile at the lowest speeds tested (3 and 7.5 m/s). The highest speeds tested (15 and 30 m/s) showed good near-wall agreement with the turbulent calculations. The streamwise turbulence intensity measured with a hot-wire probe was 0.18% at test speeds above 7.5 m/s, agree (open full item for complete abstract)

Master of Science, University of Akron, 2020, Polymer Engineering

Heat is a ubiquitous phenomenon and its spatial flow has wide reaching impact that spans industry, physiology and even meteorology through examples such as materials processing, thermotaxis and weather patterns. In fluids, spatial heat flow – temperature difference over a characteristic length scale – produces gradients in density and viscosity to generate convective currents which assuredly affects rheological properties and dynamics. The coupled effects between fluid flow and heat flow are phenomenologically explored. To achieve this, a custom-built apparatus capable of introducing, sustaining and measuring heat flux orthogonal to fluid flow was integrated into a stress-controlled rheometer to investigate the impact of steady state temperature gradients on rheological characteristics under steady shear. The novelty of this system is the capacity to independently control temperature of each rheometer plate (i.e. test surface) to establish discreet temperature gradients in the range of -16 K/mm to 30 K/mm, which also gives a window to any potential gravitational effects. Glycerol is used as a model Newtonian fluid to validate the system. Coupled dynamics is scaled by the Brinkman number and Richardson number and is found to have a linear relationship for glycerol. To expand on this knowledge, preliminary data on a more complex (non-Newtonian) system with relevance to heat transfer applications is presented. The rheological and heat flow data was presented using this approach for nanofluids of two weight fractions of Carbon Nanotubes (CNT) in glycerol in order to further understand the implications and opportunities that interrelationships between heat and fluid flow may present in a more complex system.

Master of Science (MS), Ohio University, 2020, Environmental Studies (Voinovich)

This study investigated pollinator use across areas of the channelized Hocking River's banks in different stages of ecological succession, according to when each area last experienced a mowing disturbance. These successional stages of growth—an associated pollinator use—were compared according to each area's community structure using metrics such as diversity, leaf area index (LAI), greatest height, percentage of native plants, and percentage of noxious plants. Each successional stage was monitored over time to assess seasonal change in both vegetative growth and pollinator use. Each area was also evaluated for both actual and hypothetical roughness scenarios to determine what impact mowing regimes—and lack thereof—might have on flood potential. Considerations were given to past studies that examined community perceptions of the channelized river, as well as precipitation and flood trends. Ultimately, this study investigated whether alternative mowing practices could be socially, economically, and ecologically beneficial, without jeopardizing flood protection. The study concluded that the ecosystem service benefits of actively managed growth outweigh the risk of flooding in the channel. It recommends that further studies, including a review from the Army Corps of Engineers, be undertaken to begin the process of restoring the channelized Hocking River's riparian zone to a more sustainable and ecologically beneficial state.

Doctor of Philosophy, University of Akron, 2020, Polymer Engineering

The nature of glassy aging has been a topic of study for over half a century, and yet a number of open questions remain in the understanding of the glassy state. Since a polymer's physical and mechanical properties are directly dependent on its molecular structure and changes in that structure alter the physical properties of the glass, considerable economic impact can result from aging-related physical changes. Characterization of aging dynamics in under-dense and over-dense glasses and a comparison of the aging response in solvent-processed vs thermally-quenched glasses are two important questions that are addressed here. This work reports on the development of a protocol for studying physical aging via molecular dynamics simulation after a near-instantaneous temperature quench. The resulting data display characteristic experimental signatures of glassy aging in both a pure polymer and a polymer-plasticizer system, indicating that this protocol can potentially be used to study aging in a variety of systems. Results indicate that aging dynamics in under-dense and over-dense glasses are fundamentally different in character. Unlike in under-dense glasses, translational dynamics in over-dense glasses are mechanistically different than relaxation in equilibrium glass-forming liquids, which is supported by the finding that relaxation in over-dense glasses occurs through an explosive burst of superdiffusive motion. Addition of a plasticizer appears to moderate this response compared to that of the pure polymer system, which can be attributed to a decrease in system fragility in the plasticized system. Higher additive loadings may have an even greater effect and further research would be beneficial in clarifying this. Aging relaxation time in over-dense glasses obeys a zero parameter dependence on purely equilibrium properties. This finding enables prediction of non-equilibrium relaxation time given knowledge only of the starting temperature and the in-equilibrium (open full item for complete abstract)

Master of Science, University of Akron, 2020, Civil Engineering

Low temperature cracking is a major distress for flexible pavements in cold regions. Most tests that are used currently to predict asphalt mixture performance at low temperatures require long time and effort to perform the test and analyze the data. A new laboratory test called the Ohio CTE device (OCD) has been developed as a more practical alternative to predict the asphalt mixture performance at low temperatures. This study presents an evaluation of the Ohio CTE device (OCD) in terms of effort for sample preparation, testing time, repeatability of test results, and complexity of the analysis of test data. To assess the ability of the Ohio CTE device (OCD) to predict the low temperature performance of asphalt mixtures, results obtained from this test were correlated to three other common low temperature tests, including the creep compliance and indirect tension test (IDT), the thermal stress restrained specimen test (TSRST), the asphalt concrete cracking device test (ACCD). Nine asphalt mixtures prepared using the same aggregate blend and different asphalt binders were included in this study. High correlation was observed between the Ohio CTE device (OCD) test results and results obtained from the other laboratory tests. In addition, the Ohio CTE device (OCD) was found to be advantageous over the other low temperature tests in that it requires significantly less time to prepare the test samples, which suggests that the Ohio CTE device (OCD) can be used as a routine test for low temperature characterization of asphalt mixtures.

Master of Science (MS), Ohio University, 2020, Mechanical Engineering (Engineering and Technology)

This work involved Krouse type flexural fatigue tests for 316L stainless steel, Ti-6Al-4V, and Inconel 718 at elevated mean stress. A custom machine was used to induce fatigue using a slider crank and adding an initial displacement with a micrometer for the elevated mean stress tests. The goal was to determine if there are any significant differences in fatigue life behavior for this method of fatigue testing by comparing to published axial data with elevated mean stresses. There were no significant differences found between the experimental and Goodman slopes on constant stress diagrams at 10^6 cycles for Ti-6Al-4V (p = 0.336) and Inconel 718 (p = 0.0867) at a 5% level of significance. The 316L never fractured a specimen at elevated mean stress. The data for the 316L appeared normal using a modified failure condition of formation of visible cracks as a failure/survival criterion (p = 0.722).

Doctor of Philosophy (PhD), Ohio University, 2020, Civil Engineering (Engineering and Technology)

The primary types of deterioration in skewed composite adjacent box beam bridges are cracking in the deck and longitudinal reflective cracking above the shear keys. Possible causes include early age conditions, temperature, and traffic loads. Eliminating or reducing these types of damage is expected to lead to increased service life and reduced maintenance costs for this type of bridge. In this research, a skewed composite adjacent box beam bridge built in November 2015 on Dry Creek Road in Granville, Licking County, Ohio, was instrumented with embedded and attached sensors, including strain gauges, thermocouples, and linear variable differential transformers (LVDTs). These sensors were then monitored during the construction of the bridge on-site, and service, including during arranged field tests with a controlled vehicle load. The bridge was also analyzed using a validated threedimensional finite element model (FEM). Non-uniform temperature through the bridge superstructure and shrinkage cause high tensile strains at the bottom surface of the deck during the early aging of the concrete. The highest measured strains were near the supports and parallel to the skewed angle. Radial cracks were observed at the concrete deck ten months after bridge construction. Measurements made at the box beam fabrication facility showed a lack of uniformity in beam dimensions. Even if the variation in the beam dimensions was within tolerance, there was contact between adjacent beams at isolated spots where thermal expansion led to compressive stress at contact areas. Placing box beams at a slight angle to create a transverse slope and facilitate drainage also creates potential contact areas along the bottom edges of adjacent beams. The FEM showed that under uniform temperature and temperature gradient conditions, the stresses exceeded the concrete design strength at certain contact points along the beams' length. The skew geometry had a significant effect on the distribution of stre (open full item for complete abstract)

Doctor of Philosophy, University of Akron, 2020, Polymer Engineering

In relation to traditional polymer processing techniques, 3D printing is still being established as a highly useful processing method. As the literature on 3D printing rapidly grows, public users, private companies and researchers alike are constantly learning how to improve on 3D printing methods, procedures and materials. Currently, two of the main deficiencies, which if improved, would greatly benefit fused deposition modeling (FDM) 3D printing are the print quality and mechanical properties of the objects printed. While optimization of printing parameters can facilitate some improvement of these deficiencies, objects printed via FDM printing lack the level of quality and the mechanical strength found in objects made through traditional and well - established processing methods, such as injection molding. In this work, two methods are employed to improve on part quality and mechanical properties. The first method is the use of a novel filament system which aids in filling random air gaps within objects that are FDM printed. This leads to an overall improvement of part quality as porosity decreases while the properties of the objects printed using this filament system are shown to be consistent across multiple printing conditions. The second method is the use of a structure within the FDM printed objects in order to improve impact resistance. Cellular solid structures within literature are shown to be lightweight yet mechanically strong, and therefore quite useful in a variety of applications. Printing of cellular solid structures into 3D objects greatly expands the ever - growing applications of FDM printing. Furthermore, this strategy is promising for 3D printing specifically, due to the ability to easily customize object design with rapidity. Lastly, the catalogue of materials printable via 3D printing is also consistently expanding. While network forming polymers that can be water swollen, hydrogels, have been printed in their hy (open full item for complete abstract)

Doctor of Philosophy, University of Toledo, 2020, Engineering

Using prescriptive design approaches, structures are intended to provide a life-safety level of protection that has been shown by recent natural hazard events to have limited contribution to the post-disaster resilience of a community. The performance-based engineering (PBE) methodology allows the structure to be designed to achieve any pre-defined performance objective. The structures of the future will not only aim at being structurally resilient but also sustainable to natural hazard loads. To contribute to the development of these structures, PBE requires the development of state-of-the-art numerical models for the accurate structural performance assessment and the creation of a framework that can effectively account for this performance when evaluating the environmental impacts of structures. This research has two main goals: i) to create state-of-the-art high-fidelity numerical models for the PBE of structures; and ii) to create a multidisciplinary framework for the resilient-based environmental impact assessment of structures subjected to natural hazard loads. In pursuit of this research's goals, four main objectives were conducted: High-Fidelity Numerical Modeling, PBE, Life Cycle Assessment, and Combined PBE and LCA. This research has been primarily conducted on reinforced concrete (RC) and cross laminated timber (CLT) structures, as the first is a traditional and resilient while the second is a newer and seemingly more sustainable structural alternative. However, the created approach can also be applied to other structural alternatives under natural hazard loads. The high-fidelity numerical models created have demonstrated to satisfactorily capture the structural performance of the considered building structure alternatives and the multidisciplinary framework created provides a powerful means for making science-based decisions when considering newer and seemingly more sustainable building structure alternatives while accounting for their natural hazard (open full item for complete abstract)